For example, Kompany, Arteta, Enzo Maresca and several other coaches have also succeeded but in the end, Pep himself has failed now. Thus, even other coaches who have good ideas like Pep's, but if they are not creative to always improve, then they are still likely to fail.
How has Pep failed? I don't think what Pep is experiencing at Man City currently can be called failure. He's just going through a difficult phase, which is normal for any manager. If this performance continues till next season or on to another club then you can say he's failing, but for now, he's not.
Dortmund may still have a chance to improve their position in the standings, the points difference is also not far. But for the trophy competition, I think Dortmund may be a little behind. It will be difficult for them to catch Munich who are already leading or Leverkusen.
The point difference between Dortmund who are in 6th position and the 3rd position is just 2 points so I believe if they sit up they can go higher up the table, but I agree with what you said that they can't compete for the title. Dortmund is too inconsistent to be a title contender. Even if they were just 2 points behind the league leaders I won't trust them to win the league. As an institution, Dortmund is not ready to win the league.